High-strength steel sheet and method for producing same
A technology of high-strength steel plate and manufacturing method, which is applied in the direction of manufacturing tools, furnaces, heat treatment equipment, etc., can solve problems such as difficulty in improving collision safety and formability at the same time.
Active Publication Date: 2022-04-19
KOBE STEEL LTD
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Problems solved by technology
However, the current situation is that it is difficult to simultaneously improve crash safety and improve formability even with these technologies proposed so far.
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[0156] After casting materials (steel grades A to E) having the chemical composition shown in the following Table 1 (remainder: iron and unavoidable impurities other than P and S) were produced by vacuum smelting, the steel grades were made by hot rolling. Hot rolling was further performed so that the plate thickness of the cast material became 30 mm. Ac of each steel type shown in Table 1 below 3 The transformation point is a value calculated by referring to the following formula (2) of the formula VII-20 described on page 273 of "Leslie Iron and Steel Materials Science: 1985, William C. Leslie". In addition, the column of "-" in Table 1 shows that it was not added or it was below the detection limit.
[0157] Ac 3 Phase transition point (°C) = 910-203 × [C] 1 / 2 -15.2×[Ni]+44.7×[Si]+104×[V]+31.5×[Mo]-30×[Mn]-11×[Cr]+700×[P]+400×[Al]+400 ×[Ti] formula (2)
[0158] Wherein, the above-mentioned [C], [Ni], [Si], [V], [Mo], [Mn], [Cr], [P], [Al] and [Ti] represent C, Ni, Si, ...
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Abstract
Provided are: a high-strength steel sheet which can be used in various applications such as automotive parts and has excellent collision safety and moldability; and a method for producing the high-strength steel sheet. A high-strength steel sheet according to one aspect of the present invention satisfies a prescribed chemical composition, and has a metallographic structure in which, in terms of area ratio, a ferrite fraction of 0-10%, an MA fraction of 0-30%, and a hard phase other than ferrite and MA of 70-100%, and in which, in terms of volume ratio, a retained austenite fraction of 5-30%, when crystal grains having a bcc structure and a bct structure are defined as a set of 0.05 [mu] m2 area regions, the skewness is-1.2 to-0.3 when the IQ skewness is represented by a prescribed relational expression when analyzed by the EBSD method.
Description
technical field [0001] The present invention relates to a high-strength steel sheet suitable for various applications including automobile parts. Background technique [0002] For steel sheets used in automobile parts and the like, strength is required to be increased in order to protect passengers by ensuring collision safety, reduce the weight of the vehicle body to improve fuel consumption, and reduce environmental loads. Examples of mechanical properties that significantly affect crash safety include tensile strength, yield strength, and the like. [0003] On the other hand, in order to use a steel sheet as a member for parts with complicated shapes, excellent formability is also required. Examples of mechanical properties that greatly contribute to formability include ductility, hole expandability, and bendability. However, it is difficult to improve crash safety and improve formability at the same time. [0004] So far, as technologies independent of each other, rel...
Claims
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IPC IPC(8): C22C38/02C22C38/06C22C38/04C22C38/14C22C38/12C22C38/08C22C38/18C22C38/34C22C38/38C22C38/28C22C38/26C22C38/24C22C38/22C22C38/32C22C38/58C22C38/40C22C38/50C22C38/48C22C38/46C22C38/44C22C38/54C21D8/02
CPCC22C38/02C22C38/06C22C38/04C22C38/14C22C38/12C22C38/08C22C38/18C22C38/34C22C38/38C22C38/28C22C38/26C22C38/24C22C38/22C22C38/32C22C38/58C22C38/40C22C38/50C22C38/48C22C38/46C22C38/44C22C38/54C22C38/005C22C38/002C21D8/0226C21D8/0247C21D2211/005C21D2211/008C21D2211/001C21D9/46C21D1/20C21D1/25C21D1/28C21D8/0205C23C2/04C21D2211/002C21D1/78C21D8/0236C23C2/06B32B15/013C21D6/005C21D6/008C21D8/0263C23C2/40
Inventor 村田忠夫池田宗朗村上俊夫
Owner KOBE STEEL LTD